Phenol recovery



Filed May 24, 1965 INVENTOR (l/A2455 M. 554 W/TZ United States Patent3,390,194 PHENOL RECOVERY Charles M. Selwitz, Monroeville, Pa., assignorto Gulf Research & Development Company, Pittsburgh, Pa., a corporationof Delaware Continu'ationdn-part of application Ser. No. 420,436, Dec.22, 1964. This application May 24, 1965, Ser. No. 458,070

1 Claim. (Cl. 260-621) ABSTRACT OF THE DISCLOSURE A process forrecovering phenol from admixture with a benzene compound, Water and HBr.The process involves first separating from the admixture an organicphase containing the benzene compound and a portion of the phenol and anaqueous phase containing water, the remainder of the phenol and HBr. Theaqueous phase is then extracted with a benzene compound to remove thephenol from the water. The extract is combined with the organic phaseabove and the combined product is water washed to remove residualamounts of HBr. The waterwashed product is then distilled to recover thephenol.

This is a continuation-in-part application of my application Ser. No.420,436, entitled, Process, which was filed on Dec. 22, 1964.

Briefly, application Ser. No. 420,436 relates to a process for oxidizinga benzene compound, such as benzene itself, to the corresponding phenolwhich comprises, for example, reacting in the vapor phase at atemperature of about 600 to about 800 C. a benzene compound with about0.02 to about five mols thereof of oxygen in the presence of about 0.5to about 50 mols thereof of water and about 0.0001 to about 0.20 molsthereof of a compound selected from the group consisting of HBr and acompound capable of resulting in the formation of HBr under theconditions of reaction, such as 1,2-dibro-momethane, tertiary butylbromide or tertiary amyl bromide.

This invention relates to a process for recovering the desired phenolfrom the reaction product obtained as a result of the process definedand claimed in application Ser. No. 420,436, particularly in therecovery of phenol free of HBr. Not only can HBr so recovered be reusedin the oxidation of the benzene compound to obtain the correspondingphenol, but its presence with phenol is undesirable, since it has atendency to lead to the decomposition of the phenol during itssubsequent distillation.

The process defined and claimed herein can be understood by reference tothe accompanying drawing which described a preferred embodiment thereof.The recovery of phenol from a reaction product obtained as a result ofthe oxidation of benzene will be described, but it is understood thatthe same recovery and purification system can also be employed torecover other purified phenols from mixtures resulting from theoxidation of other benzenes. In the drawing the reaction mixtureproduced in application Ser. No. 420,436, cooled to a temperature ofabout 0 to about 70 C., preferably to a temperature of about 20 to about30 C., by any suitable means, is introduced into the system by line 2.The mixture in line 2 can contain, in parts by weight from about 1 toabout 100 parts of benzene; about one to about 50 parts of phenol; about35 to 500 parts of water; at least about 0.01 part of HBr, but generallyabout 0.2 to 16 parts of HBr; about 0.6 to about 160 parts of oxygen;about 0.01 to about 100 parts of by-product gases, such as carbonmonoxide and carbon dioxide; and about 0.01 to about 20 parts of highermolecular weight compounds, such as biphenyl, etc.

3,390,194 Patented June 25, 1968 The mixture in line 2 is introducedinto separator 4 which can be maintained at a temperature of about 0 toabout 40 C., preferably about 15 to about 25 C., and a pressure of about0.10 to about 100 atmospheres, preferably about one atmosphere. Themixture in separator 4 resolves itself into a lower aqueous layer, anupper organic layer and gases. The gases are removed overhead by line 6and can be recycled as such, or preferably, after removal of carbonmonoxide and carbon dioxide therefrom, to the oxidation stage whereinbenzene is oxidized to phenol.

The lower aqueous phase, containing most of the HBr and from about 20 toabout 50 percent by weight of the phenol in separator 4, is removed fromseparator 4 by line 8 and is passed to extraction tower 10 which ismaintained at a temperature of about 0 to about C., preferably about 15to about 25 C., and a pressure of about 0.10 to about atmospheres,preferably atmospheric pressure. Benzene is introduced by line 12 intoextraction tower 10 adjacent the base thereof and is passed upwardlytherethrough countercurrent to the movement of the aqueous phasetherein. The benzene to aqueous phase weight ratio in extraction tower10 is maintained within a range of about 1:1 to about 10:1, preferablywithin a range of about 2:1 to about 5:1. As a result of theseconsiderations there is removed from the base of extraction tower 10 byline 14 water, substantially all of the HBr and trace amounts of phenol.This stream can be discarded, if desired, but preferably it is recycledto the oxidation stage wherein benzene is oxidized to phenol. Ifdesired, the HBr can be reacted with an organic compound, such as anolefin, to obtain an alkyl halide which can be employed in the aforesaidoxidation stage. There is removed overhead from extraction tower 10 byline 16 benzene and substantially all of the phenol that was present inthe aqueous phase.

The. organic phase in separator 4 containing benzene, phenol and thehigher boiling organic products is removed from separator 4 by line 18,combined with the mixture in line 16 and the combined product passed towater washer 20. Water in an amount of about 0.1 to about 20 percent byweight, preferably about one to two percent by weight, based on thebenzene, is introduced into water washer 20 by line 22. The temperaturein water washer 20 can be maintained from about 0 to about 40 C.,preferably from about 15 to about 25 C., and the pressure from about0.10 to about 100 atmospheres, preferably at about one atmosphere. Thepurpose of the water is to remove any residual traces of HBr from theorganic phase in water washer 20. The water containing HBr is removedfrom the base of water washer 20 by line 24 and can be discarded or, ifdesired, can be recycled to the oxidation stage previously described.

The remainder of the product is removed from water washer 20 by line 26and passed to a distillation column, or other suitable distillationzone, 28, which can be maintained at a temperature of about 20 to about300 C., preferably about 60 to about 200 C., and a pressure of about 10-to about 30 pounds per square inch gauge, preferably about one to about15 pounds per square inch gauge. Pure benzene is removed overhead byline 30, pure phenol by line 32 and heavier products, which can bediscarded, by line 34. The benzene in line 30 can be recycled to theoxidation zone to produce additional phenol.

The process defined herein can further be understood by the following.Into a calorized reactor (one having an aluminum oxide internal surface)which was 24 inches high and had an internal diameter .of one'inch, andwhich was maintained at atmospheric pressure, there was continuouslyadded 6.4 rnols per hour of water, 0.0029

mol per hour of HBr (dissolved initially in the water), 0.86 mol perhour of benzene and 0.45 mol per hour of oxygen. The temperaturethroughout the reactor averaged 682 C. and the highest temperaturereached therein was 684 C. The product from the reactor was cooled to atemperature of 25 C. over a period of one hour. The upper layer,containing 49 grams of benzene, 3.9 grams of phenol and smallerquantities of biphenyl and other byproducts, was separated from thelower layer, containing 115 grams of Water, 0.23 gram of HBr and 3.6grams of phenol. The aqueous phase was extracted with 200 grams ofbenzene at 25 C. The organic phase resulting from this extraction,containing about 200 grams of benzene and three grams of phenol wasadded to the benzene phase originally separated from the reactionproduct. The extracted aqueous phase containing the HBr and .a trace ofphenol was recycled to the oxidation stage. The combined benzene phaseswere extracted with cc. of water at 25 C. to remove traces of HBrtherein. The remainder of the material was then distilled at atemperature of 70 to 200 C. to obtain 249 grams of benzene, 6.5 grams ofphenol and a small amount of distillation bottoms. The purificationprocedure described above was carried out at atmospheric pressure.

Obviously many modifications and variations of the invention, ashereinabove set forth, can be made Without departing from the spirit andscope thereof, and only such limitations should be imposed as areindicated in the appended claim.

I claim:

1. In a process wherein benzene is reacted in the vapor phase atelevated temperatures with oxygen in the pres ence of water and acompound capable of resulting in the formation of HBr under theconditions of the reaction to obtain a reaction mixture containingphenol, benzene, water, HBr and oxygen, the improvement in recoveringphenol free of HBr from said mixture which comprises separating fromsaid mixture .at a temperature between 0 and C. an organic phasecontaining said benzene and a portion of said phenol, an aqueous phasecontaining water, the remainder of said phenol and HBr and oxygen,extracting said aqueous phase with benzene at a temperature between 0and C. to obtain an extract containing benzene and said remainder ofsaid phenol, combining said extract and said organic phase, washing thecombined product so obtained with water at a temperature between 0 and40 C. and to remove residual amounts of HBr, separating said combinedproduct from said water and thereafter separately recovering phenol andbenzene from said combined product by distillation.

References Cited UNITED STATES PATENTS 3/1936 Prahl et al. 260621 OTHERREFERENCES Kleinberg, J., et al., Inorganic Chemistry, Heath & Company,Boston, 1960, pp. 4701.

BERNARD HELFIN, Acting Primary Examiner.

LEON ZITVER, Examiner.

H. ROBERTS, Assistant Examiner.

